Method oe cohstguctotg pistosts



C. WERRA.

METHOD OF CONSTRUCTING PISTONS.

APPLICATION FILED SEPT- 25, I914- Patented Aug. 22, 1916.

' [N VEN TUF? .HJLLL M T/VE 555 5 A TTURNEYSI GONRAD WERRA, F WAUKESHA, WISCONSIN.

METHOD OF CONSTRUCTING PISTONS.

original application filed June 18,

Specification of Letters Eatent.

Patented nag. as, rare.

1914, Serial No. 845,774. Divided and this application filed September 25, 1914. Serial No. 883,482.

To all whom it may concern."

Be it known that I, CONRAD WERRA, a citizen of the United States, and resident of lVaukesha, in the county of Waukesha and State of Wisconsin, have invented new and useful Improvements in Methods of Constructing Pistons, of which the following is a description, reference being had to the accompanying drawings, which are a part of this specification.

' This invention relates to improvements in the method of constructing pistons, the present application being a division of my application on piston construction, Serial No.

845,774, filed June 18th, nut.

in the manufacture of internal combustion engines the tendency is toward light.

weight high speed engines. In engines of this type the cylinders and pistons are usually formed of iron and are therefore comparatively heavy and considerable power is lost in overcoming inertia of movement of the heavy piston at the end of each reciprocation.

A further objection to pistons formed of iron or like material is that the weight causes unnecessary vibration which increases the wear on the parts and thereby consumes additional power.

It is one of the objects of the present invention to overcome the before mentioned objectional features and provide a method of constructing pistons whereby pistons may be formed which are of less weight than the pistons now in use, and in which provision is made for taking the wear of the parts thereof.

A further object of the invention is to provide a method of constructing pistons whereby the major portion of the piston may be formed of aluminum or other light weight metal protected with other subjected to greatest wear.

A further object of this invention is to provide a method of constructin pistons in which parts are adapted to con ormto the irregularities in shape of the inner wall of the cylinder of the engine of which the piston forms a part. y

A further object of the invention is to metal at points piston.

ofexpansion whereby provision is made for permitting the unequal expansion of metals while the piston is in use.

With the above and other objects in view the invention consists in the improved method of constructing pistons as set forth in the claims.

In the accompanying drawing in which the same reference characters indicate the same parts in all of the views, Figure 1 is a sectional view of a portion of a mold illustrating the method of forming the piston of a plurality of different metals, the bearing rings being shown in position before casting the body portion therearound; Fig. 2 is a longitudinal sectional view of the completed piston; Fig. 3 is a transverse sectional view thereof taken on line 33 of Fig. 2; and Fig. 4 is a side view of the complete piston. Referring to the drawing numeral 5 indicates the body portion of the shell of the piston which is formed of aluminum or other light weight metal, and is provided with the usual inwardly extending bored bosses 6 to receive the cross pin to which the connecting rod is pivotally mounted, The bosses are reinforced by ribs 7 which extend upwardly and connect with the top or end wall 8 of the piston. ()ne of thebosses is provided with a threaded opening 9 to receive a set screw for clamping the connecting rod cross pin in position. This end wall is of convex form to better resist the strain of the explosion. lhe piston is cast partly around unbroken bearing rings 10 and 11 preferably of iron which are of. slightly arger diameter than the piston in order to engage the surface of the bore of the cylinder. The rings 10 are of rectangular form in cross section and fit snugly in the grooves 12 formed'in casting the piston.

The inner upper portion of the bearing ring 11 is also of substantially rectangular form in crom section with a flanged bearing portion 13 extending toward the open end of the piston. The ring also fits snugly within a oove 14: formed in casting the ring 11 is provided with annuice la r grooves 15, to receive split piston packing rings of ordinary construction. I

- n casting the pistons, the rings are cut to size and shape and are then placed in their respective positions in a die or sand mold 16 as indicated in Fig. 1 and the molten aluminum orother light weight metal is then poured into the casting space 17 formed in the mold and in filling the space the metal will engage the exposed inner'and portions of the upper and lower surfaces of the bearing rings 10 and 11.

'As the coeflicient of expansion of aluminum is greater than iron the aluminum in cooling in the mold Will contract and draw away from the inner surfaces of the bearing rings and form annular spaces 18 as shown in Figs. 2 and 3 which will permit the expansion of the piston when doing its work within the cylinder without unduly straining the packing rings.

, It is a known fact that the cylinder bores of the engines become distorted and out of trueafter being bored and olished due to the varying thicknesses of t e metal formingthe walls of the cylinders and consequently when the istons are mounted withi in the cylinders t ey will only engage portions of thecylinder walls. The annular expansion spaces 18 permit the bearingrings to yield slightly and conform to the irregularities of the cylinder walls and thus eliminate undue friction and wear.

The light wei ht of the piston due to the major portion 0 the metal being aluminum re uiresless power to reciprocate itback an forth and vibration is therefore reduced to the minimum.

From the foregoin description it will be seen that the metho of constructin pistons provides a light weight piston a apted for the purpose sesses the necessary strength to withstand a piston shell of metal of gr the wear it is subject to.

What I claim as my invention is: 1. A method of constructing pistons of two metals of different degreesof coefficient of expansion, consisting of finishing the portion of lesser expansibilit and casting a portion ofater expansi ility within the portion of esser expansibility and in engagement therewith and permitting the contraction of the cooling cast metal to wlthdraw radially' therefrom to provide spaces for the, expansion of said portion 'ofgreater I 'expansibillty.

2. A method of constructing pistons of two metals of di erent' de eesof coefficient of expansion, co sisting o finishin a bearing ring of lesser expansibility an castmg eater expansibllit within the ring and in engagement with t e inner ahd portions of the edge surfaces of said ring and permitting the conto wit escribed and which pos-.

traction of the cooling shell to withdraw radially from the innerfsurface of the ring to provide a space for permitting the exp nsion of the shell. 4

3. A method of .constructmg pistons of two metals of different degrees of coefficient of expansion, consisting of placing a plurality of unbroken bearing rings of lesser expansibility in spaced relation within a mold and casting a piston shell of metal of greater expansibility within the rings and mold and casting a piston shell of metal of greater expansibility within, the rings and in engagement with the inner and portions of the edge surfaces of said'rings and ermitting the contraction of the cooling s ell to withdraw radially from the inner surface of the rings to provide spaces between the inner peripheries of the rings and the mately parallel e gl a faces which are engaged by portions of the shell and one of the said rings havin an annular recess for receiving a split pac 'ng rin 5. A method of constructmg pistons of dissimilar metals, which consists in placing bearing rings in av mold, then pouring a dissimilar molten metal into the mold to shell for permitting radial expansion of the shell, said bearin having approxiform a piston shell which partly surrounds v the bearing rings and non-adherently holds them in position, the metal of-the.piston shell havmg a greater coefiicient of expansion than the rings and withdrawing radially therefrom in cooling to provide space to (permit' of the greater expansibility of sa1 piston shell.

6. A method of constructing pistons of dissimilar metals, which consists in placing 1ron bearing rings in a mold, then pouring aluminum in a molten state into the mold to v form a piston shell which partly'surrounds the bearing rings and non-adherently holds them in position, the metal of the piston shell having a greater coeflicient of expans1on than the rings andwithdrawing therefrom radially to provide space to ermit of the greater ex ansibility of said s ell.

7. A metho of constructing pistons of j dissimilar metals, which consists in placing iron bearing rings in a mold, one of said rings having an annular: groove for receiving a, packing ring, then pouring aluminum in a molten state into the mold to form a, piston shell which partly surrounds the bearing rings and non-adherently holds them in position, the metal of the-aluminum shell having a, greater coeficient of expansion than the iron of'the bearing rings and withdrawing radially therefrom to provlde CONRAD WERRAQ Witnesses:

A. C. PANKRATZ, 

